Chunhua Zhao

Selenium-Doped Silicon-on-Insulator Waveguide Photodetector With Enhanced Sensitivity at 1550 nm

This letter describes the fabrication and characterization of a silicon-on-insulator all silicon rib waveguide photodetector with sensitivity at 1550 nm. Response at the subbandgap wavelength is provided through the introduction of deep levels via Se ion implantation. Se ions were implanted into the waveguide using an ion beam energy of 240 keV at a dose of 3×1015 cm-2. The most efficient device has a responsivity of 25 mA/W at 3 V reverse bias. The fabrication is fully compatible with standard complementary metal-oxide-semiconductor processes.

Deep Energy Levels Formed by Se Implantation in Si

To transfer a photon with a 1.55μm wavelength into an electron in an integrated optoelectronic silicon waveguide detector, selenium-doped silicon with deep energy levels is used. The deep levels in the silicon with implanted selenium are studied. Three levels are observed and their captured cross sections, concentrations and in-depth profiles are measured.

Optical response of high-level bandgap in one-dimensional photonic crystal applying in-plane integration

A new broadband filter, based on the high level bandgap in 1-D photonic crystals (PCs) of the form Si|air|Si|air|Si|air|Si|air|Si|air|Si is designed by the plane wave expansion method (PWEM) and the transfer matrix method (TMM) and fabricated by lithography. The optical response of this filter to normal-incident and oblique-incident light proves that utilizing the high-level bandgaps of PCs is an efficient method to lower the difficulties of fabricating PCs, increase the etching depth of semiconductor materials, and reduce the coupling loss at the interface between optical fibers and the PC device.

Investigation of diffusion length distribution on polycrystalline silicon wafers via photoluminescence methods.

Characterization of the diffusion length of solar cells in space has been widely studied using various methods, but few studies have focused on a fast, simple way to obtain the quantified diffusion length distribution on a silicon wafer. In this work, we present two different facile methods of doing this by fitting photoluminescence images taken in two different wavelength ranges or from different sides. These methods, which are based on measuring the ratio of two photoluminescence images, yield absolute values of the diffusion length and are less sensitive to the inhomogeneity of the incident laser beam. A theoretical simulation and experimental demonstration of this method are presented. The diffusion length distributions on a polycrystalline silicon wafer obtained by the two methods show good agreement.

Self-assembling of submicrometer three-dimensional photonic crystals in concave microzones etched on silicon substrates

By vertical sedimentation and oblique titration, silica microspheres were grown in different shapes of concave microzones that were etched on a (100) p-silicon substrate. Through scanning electron microscope observation and optical reflective spectra measurement, sedimentation of microspheres in those microzones was compared. An index was introduced to judge the efficiency of sedimentation. The comparison demonstrates that regular hexagons and triangles facilitate the growth of photonic crystals the most.

Micro-mould method for self-assembling three-dimensional opal photonic crystals

By vertical sedimentation, silica micro-spheres were grown in different shapes of concave micro-zones which were etched on a (100) p-silicon substrate. The following were found: this method can effectively raise the quality of films by avoiding cracks; the geometry of the micro-zones affects the sediment of the film; regular hexagons and triangles best facilitate the growth of photonic crystals. This method is practical for its ability to fabricate self-assembly photonic crystals in previously designed small areas.

Formation of absolute PBG of 2D square lattice by changing the shapes and orientations of rods

In this paper, the effects of shapes and orientations of rods on absolute PBGs in 2D square lattice are studied. By replacing round rods with square rods, which sides are along with the direction of elementary lattices vectors, the absolute PBGs in 2D square lattice with wave vector in periodic plane and off pericdic plane have been studied and then through changing the square rods orientation, the changing of the width and position of PBG has been obtained.